Tick based audio and time stretching

[gdgross]

Hi all. Have a song that was tracked at ~140bpm with just bass and drums, with scratch guitar and scratch vocals. (I say ~ because the tempo map had a few minor accelerandos and the verses were a one or two bpm slower than the choruses.)

After tracking bass & drums, I felt that the tempo was a bit on the lopey side so i converted all tracks to tick based, and bumped the tempos of the various section up a few clicks.

To my ears, it mostly sounds transparent. Where i notice the biggest artifacts are in the accelerandos in the guitar and the vocals (which are fortunately, the temp tracks anyway)

Do you all have the same experience? What are the limits of tempo changes in tick-based audio before you start to hear it? And, should I convert back to sample based once the tempo is set? I did hear a couple spots that could use a little editing love.

This is the first time I've used tick based audio, by the way. I think it sounds better than the time compression/expansion, but I could be imagining it, and can't hear a difference either way when I shift only a few bpm. hah.

Thanks!!

[Rich Breen]

Elastic Audio is capable of excellent results in most cases, but performance is rarely very good without attention to detail; you have to be sure to be using the correct engines for the type of track you're working with, and one really needs to go through and pay attention to analysis markers; getting rid of unnecessary ones, setting sensitivity, etc. Xform will give much better results once the details are finalized and you can render the whole thing.

In short - if you just turn EA on and then start changing tempos, it's decent for a rough draft, but for final quality the devil is in the details. And yes, generally when a piece is "finished" I think it's a good idea to render all your EA tracks (after saving in their current state for later editing).

[gdgross]

Thanks Rich. I didn't edit any elastic audio markers, but I can go through and do that. Sounds pretty good to me though as is, at least on the tracks I'm keeping. I guess it's worth checking that that PT detected/assigned the marker locations properly before converting back to sample
Based.

By xform you mean what I did?

[Rich Breen]

Originally Posted by gdgross

...I guess it's worth checking that that PT detected/assigned the marker locations properly before converting back to sample Based.

well, if you don't hear a problem then don't worry about it, but removing unnecessary analysis markers and/or paying attention to EA's detection sensitivity can often get rid of a lot of artifacts.

By xform you mean what I did?

I don't know what you did. The X-form algo is rendered only and *very* slow, but it usually provides the best results if you're working with delicate material. If it's something like an acoustic piano or guitar I'll often edit in "Polyphonic" and when I'm satisfied, change the algo to X-form and render it.

[gdgross]

THanks again Rich. I think I will go through and edit the elastic markers just for good measure, just to be safe.

On question. the two instrument are bass and drums - bass is two grouped tracks (DI and amp) and drums is several grouped tracks. I notice that PT doesn't assign the elastic markers the same on all tracks within the group.

For example, the inital transient of one close mic'd drum track might precede the same sound in the overheads by a msec. Will this be a problem?

THanks

[soybalm]

For drums, before you use EA or any editing, you want to group the clips. This is not the same as track groups. select all the drum clips and then in the Clip menu, select group. Any editing happens to all the tracks and in theory keeps all the drums locked in with sample accuracy. With EA, don't be surprised if you run into other artifacts. I've also ran into stubborn clips that won't group. It's probably an error on my part.
You should try to read up on it for key commands etc. to temporarily ungroup a clip to perform a different edit.

[gdgross]

Thanks soy -

I've never used clip groups before, although I use track groups every day hah. And key shortcuts for editing warp markers are invaluable- saves a ton of time vs right clicking and selecting every single one i want to change!

Two basic questions:

1. Do all my warp markers need to align at the same instant in multi-tracked instrument? for example, is it ok for the warp marker for a snare hit on the snare track to be slightly ahead of the warp marker for the same snare hit in the overhead tracks? Or is it ok as long as they are aligned with the transients in the single track itself?

2. How does one convert back to normal, sample-based, non EA audio tracks? Ive got my tempo change and everything seems to sound good right now. Is it as simple as changing the algorithm to x-form, and switching back to sample based on each track/group? I tired this and noticed that the audio disappears, although the waveform remains and turns gray, vs the usual darker version of the track color.

Thanks!

[Rich Breen]

Originally Posted by gdgross

...
1. Do all my warp markers need to align at the same instant in multi-tracked instrument?...

Yes they do. e.g. for drums I will often suspend groups and remove all the analysis markers from all the tracks except kick and snare, paying close attention to detection sensitivity, then enable groups, then add and move warp markers around as necessary.

2. How does one convert back to normal, sample-based, non EA audio tracks? Ive got my tempo change and everything seems to sound good right now. Is it as simple as changing the algorithm to x-form, and switching back to sample based on each track/group? I tired this and noticed that the audio disappears, although the waveform remains and turns gray, vs the usual darker version of the track color...

Xform will render and will take a long time; if the track is "gray" and no waveform is displayed it means it has not completed the render (keep your task manager window open and you'll see what's happening). But Xform isn't disabling EA, it's just rendering the track - if you make any change to tempo or edit an Xform-ed track you'll have to wait while it re-renders. To render a track back to non-EA you can just pull the algorithm select menu to off; Pro Tools will ask if you want to lose your EA work or commit it - obviously you'd commit it. Now the audio will be committed as a new audio file.

Strongly recommend you read the Elastic Audio section of the Reference Guide. All this is clearly spelled out.

[gdgross]

AH, thanks rich. Makes sense, my computer fans were spinning when the tracks were gray.

I'll check out the user guide as well. I may need to go back and redo the warp markers then, as I didn't force them all to the same instant, but I didn't hear anything funny. Haven't listened in solo all the way though yet though. Should be easy enough to go back and edit if i need to though.

Thanks for all your help. First time using EA for me, other than quick stupid stuff with the TCE tool.